Methods of fabricating a large area transducer array

ABSTRACT

Methods of fabricating a tiled transducer array are disclosed. Embodiments of the methods include fabricating a wafer comprising a plurality of transducers, dicing the wafer to form individual transducers, testing the individual transducers to identify a plurality of known good transducers, preparing a substrate having a front side and a backside wherein the backside of the substrate comprises a plurality of connectors, positioning the plurality of known good transducers on the front side of the substrate and aligning the plurality of transducers in a horizontal direction and a vertical direction to form a transducer array, and electrically coupling the connectors on the substrate to the plurality of known good transducers, wherein the connectors are arranged such that each of the plurality of known good transducers may be electrically coupled to an electronic device disposed on the backside of the substrate, through a respective one or more of the plurality of connectors.

CROSS REFERENCE TO RELATED APPLICATIONS

The present patent application is a divisional of, and claims priorityto, the non-provisional patent application Ser. No. 11/003,054 filed onDec. 3, 2004 and titled “Large Area Transducer Array”.

BACKGROUND

The present invention relates generally to the field of transducerarrays, and more specifically to engineering transducer arrays.

Transducers are devices that transform input signals of one form intooutput signals of a different form. Commonly used transducers includelight sensors, heat sensors, and acoustic sensors. An example of anacoustic sensor is an ultrasonic transducer. In ultrasound devices, thetransducers transform signals of electrical energy into acoustic energyor produce electrical signals from absorbed sound waves.

Various applications, such as biomedical non-invasive diagnostics andnon-destructive testing (NDT) of materials entail the use of transducerarrays, where the transducers are often configured in two-dimensions(that is, the X-Y plane). For example, ultrasonic transducer arrays areused in medical imaging, non-destructive evaluation (NDE) and otherapplications.

Applications such as medical and industrial imaging, NDE, security,baggage scanning, astrophysics and medicine may entail the use oftransducers that encompass large areas. In the field of medicaldiagnostics, such as, but not limited to ultrasound and mammography, itmay be desirable to employ transducers that encompass large areas. Forinstance, in an x-ray imaging system, large area transducers may benecessary to encompass the area of the x-ray detector.

In the field of NDT many inspection methods utilize a single contactsensor that only interrogates a small area of the structure. Generally,a skilled operator places the sensor on the structure and interprets theresulting waveform in order to detect defects. As a consequence,inspection of large areas may be extremely time consuming and defectdetection may be difficult for structures that have a complex geometry.Despite recent advances in robotic scanning technology there exists aneed for large area scanning systems.

The prerequisites for each application necessitating the use of largearea transducers differ in size and shape. The complexities and costsassociated with building a single transducer to encompass a large areacan be very significant. Furthermore, there are limitations of themanufacturing technologies with regard to the maximum size of the largearea transducer that can be profitably manufactured. Additionally, theexpenses incurred while repairing the large area transducers may beconsiderable.

Arrays of transducers may be utilized to circumvent the problemsassociated with employing single large area transducers. The X-Y planemay be employed for assembling the transducer arrays to facilitate theconstruction of large area transducer arrays. However, such arrays canbe very dense and necessitate a large quantity of control and amplifierelectronics to drive the individual transducers of the array. Presently,the control and amplifier electronics employed to drive the individualtransducers are also positioned in the X-Y plane resulting in a largefootprint and potentially, gaps in the transducer area due to the needto locate electronics in or adjacent to the transducer. Furthermore, thedensity of input/output (I/O) required for coupling the individualtransducers with the associated electronics may be very high. Also, thedensity of I/O may be too large for traditional interconnect strategiesto handle. Presently, the interconnect lengths required to couple thetransducer elements to the electronic device are very long. It would bedesirable to minimize interconnect lengths in order to circumventproblems associated with longer interconnect lengths, such as, effectsof capacitance, and degraded signal quality.

It would therefore be desirable to assemble large area transducer arraysin order to circumvent associated problems, such as, complexities andcosts associated with manufacturing and repairing a single large areatransducer. Furthermore, it would be desirable to position theassociated electronics in close proximity to the individual transducerelements of the transducer array in order to minimize system size,complexity, interconnect lengths and enhance the performance of thetransducer arrays.

BRIEF DESCRIPTION

Briefly, in accordance with one embodiment of the present technique, atransducer array is presented. The transducer array includes a substratecomprising a front side and a backside, a plurality of transducersdisposed on the front side of the substrate and aligned in a horizontaldirection and a vertical direction to form a transducer array, whereeach one of the plurality of transducers is configured for sensing acorresponding input signal and a plurality of connectors disposed on thebackside of the substrate where the connectors are electrically coupledto the plurality of transducers.

According to another aspect of the present technique, a method forfabricating a tiled transducer array is presented. The method comprisesfabricating a wafer comprising a plurality of transducers, dicing thewafer to form individual transducers, testing the individual transducersto identify a plurality of known good transducers, preparing a substrateincluding a front side and a backside, where the backside of thesubstrate comprises a plurality of connectors, positioning the pluralityof known good transducers on the front side of the substrate andaligning the plurality of transducers in a horizontal direction and avertical direction to form a tiled transducer array, and electricallycoupling the connectors on the backside of the substrate to theplurality of known good transducers.

According to a further aspect of the present technique, a stackedtransducer array is presented. The stacked transducer array includes anelectronic device disposed in a first layer and coupled to a pluralityof transducers, where the electronic device is configured for processinga plurality of input signals, a substrate disposed in a second layer andincluding a front side and a backside, an electrical interconnect layerdisposed on the substrate, and a plurality of transducers disposed in athird layer, the plurality of transducers configured for processing aplurality of input signals.

In accordance of another embodiment of the present technique, a methodfor fabricating a stacked transducer array is presented. The methodincludes fabricating an electrical interconnect on a substrate having afront side and a backside, disposing a plurality of transducers on thefront side of the substrate, and coupling the plurality of transducerson the front side of the substrate to an associated electronic device.

According to another aspect of the present technique, a method foraligning a plurality of electronic devices with a plurality oftransducers in a transducer array formed in an X-Y plane is presented.The method includes positioning each of a plurality of electronicdevices in a pre-determined direction, aligning the each of theplurality of transducers with a corresponding one of the plurality ofelectronic devices via a pre-fabricated spacer, and coupling each of theplurality of electronic devices to the corresponding transducer of thetransducer array via an interconnect.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view illustrating the patterning of transducerson a substrate, according to one aspect of the present technique;

FIG. 2 is a perspective view of one embodiment of a tiled transducerarray employing an interposer, in accordance with another aspect of thepresent technique;

FIG. 3 is a perspective view illustrating a first side of the interposershown in FIG. 2;

FIG. 4 is a perspective view illustrating a second side of theinterposer shown in FIG. 2;

FIG. 5 is a perspective view illustrating the stacking of an electronicdevice on the transducer array assembly exemplified in FIG. 2, accordingto a further aspect of the present technique;

FIG. 6 is a perspective view illustrating the stacked assemblyexemplified in FIG. 5 where the electronic device is illustrated as astack of electronic devices, according to yet another aspect of thepresent technique;

FIG. 7 is a diagrammatical view illustrating an embodiment for thestacking of electronic devices in the Z-direction; and

FIG. 8 illustrates steps for aligning the transducer elements and theassociated electronic devices, according to an aspect of the presenttechnique.

DETAILED DESCRIPTION

Turning now to the drawings, and referring to FIG. 1, a transducer array10 that may be used with a system, such as, but not limited to anultrasound scanner or an x-ray detector, is illustrated. In theillustrated embodiment, the transducer array 10 may be used to sense aplurality of input signals.

In a presently contemplated configuration, as shown in FIG. 1, thetransducer array 10 is illustrated diagrammatically as including asubstrate 12. The substrate 12 has a front side 14 and a backside 16.Typically, the substrate may include a semiconductor material, such assilicon, or a flexible material, such as polyimide, although other typesof materials with similar properties may be used.

Transducers are devices that are generally used to convert at least oneof a sound, a temperature, a pressure, a light or other signal to orfrom an electronic signal. In the exemplary embodiment illustrated inFIG. 1, the transducer array 10 includes a plurality of individualtransducers 18 configured to sense a plurality of input signals disposedon the substrate 12. For example, transducers 18 that make up thetransducer array 10 may include a plurality of sensor devices, such as,but not limited to, a photodiode, a back-illuminated photodiode, anacoustic sensor, a temperature sensor, or an electromagnetic radiationsensor. Additionally, the transducer elements may also includemicro-electro-mechanical systems (MEMs) devices, such as, but notlimited to, capacitive micro-machined ultrasonic transducers (cMUTs).

Tiling is an approach that offers an attractive solution to the problemsassociated with building a large area transducer. An exemplarytransducer array, according to the present technique may be constructedby tiling smaller, individual transducer elements 18 to form a largearea (X, Y) transducer array.

According to one embodiment of the present technique, a wafer includinga plurality of transducer elements is fabricated. The wafer is thendiced to form individual transducer elements. The individual transducerelements are then tested and known good transducers are identified asthe transducer elements 18 that may be advantageously implemented tobuild the large area transducer array.

In the illustrated embodiment of FIG. 1, X, Y and Z directions arerepresented by reference numerals 20, 22 and 24 respectively. Theplurality of transducer elements 18 is disposed on the front side 14 ofthe substrate 12 and is aligned in a row along the horizontal,X-direction 20. Additionally, a plurality of transducer elements 18 isalso disposed on the front side 14 of the substrate 12 and is aligned ina column along the vertical, Y-direction 22. In a present configuration,the plurality of transducer elements 18 is patterned in rows and columnsin the X-Y plane to form a tiled transducer array 26. The transducerelements 18 may also be electrically coupled to one another in thehorizontal 20 and vertical 22 directions. Consequently, disposing aplurality of transducer elements 18 adjacent to one another in a gridpattern results in a large area transducer array that may be employed toenvelope a larger area. For example, the large area tiled transducerarray 26 may be utilized to image a large area. Further, while thepresent exemplary embodiment illustrates transducer elements disposed onthe substrate, in an alternate exemplary embodiment, the transducerelements may be disposed to form a planar surface of transducers thusminimizing the height of the package.

Alternatively, the transducer array 10, illustrated in FIG. 1, may beconstructed during the fabrication process. During the fabricationprocess, individual transducer elements 18 may be arranged in rows andcolumns to form a monolithic transducer array.

As previously described, in one exemplary embodiment, the substrate 12may be fabricated using semiconductor materials. A multi-layerelectrical interconnect may be fabricated directly on the semiconductormaterial. As will be appreciated by those skilled in the art, traces andvias electrically isolated by dielectric materials may be disposed andetched to provide electrically conductive paths among the plurality oftransducer elements 18. The transducer elements 18 may be arrangeddirectly on top of the multi-layer electrical interconnect on thesemiconductor wafer. The transducer array 26 that has been arranged onthe electrical interconnect on the semiconductor wafer may be thinned toexpose the bottom layer of interconnect, thus making the transducerarray 26 a flexible transducer array with input/output (I/O) on backside16. Alternatively, through-wafer vias may be drilled through thesubstrate wafer 12 in order to electrically couple the transducerelements 18 present on the front side 14 of the substrate 12 to thebackside 16 of the substrate 12, thereby providing conductive paths fromthe transducer elements 18 to the backside 16 of the substrate 12. Insuch an instance the transducer array 26 does not require thinning andmay remain rigid for a planar transducer array. Another alternate methodis to achieve backside I/O by disposing interconnect on each of the foursides of the monolithic or tiled transducer array. This wrap-aroundinterconnect is disposed around the four sides of the transducer array10 and brought down along the sides and electrically coupled to thebackside 16 of the substrate 12.

In another embodiment of the present technique, the substrate 12 maycomprise a flexible material that has been adhered to a flat substrateor a semiconductor wafer for planarity. A multi-layer interconnect maybe built on the flexible material. The transducers 18 may then beassembled on top of the interconnect layer. Once the transducers 18 areassembled, the flexible material may be separated from the flatsubstrate to provide a flexible transducer array. The flexibletransducer array can conform to any shape the integrated electronicstake.

In both the flexible and semiconductor wafer interconnect methods theinterconnect side, that is the backside 16 of the transducer array 26,may be fabricated to facilitate interconnect such that individualintegrated electronic devices may be attached to the transducer usingsolder, conductive bump, wire bond, or some means of electricalinterconnect and assembly.

A plurality of connectors is disposed on the backside 16 of thesubstrate 12. The connectors may include I/O connectors that facilitatethe processing of a plurality of signals. Additionally, the connectorsare electrically coupled to the transducers 18 disposed on the frontside 14 of the substrate 12. The electrical coupling between theconnectors and the transducer elements 18 may be achieved by methodssuch as, but not limited to, through-hole vias, buried I/O that areexposed following thinning of the transducer or substrate, andwrap-around interconnect as formed by disposing electrical conductors onthe edges of the monolithic or tiled transducer arrays.

FIG. 2 illustrates another exemplary embodiment 28 of the presenttechnique. In FIG. 2, the transducer array 26 is shown including aninterposer 30. The interposer is configured to facilitate electricalcoupling between the plurality of transducers 18 and an electronicdevice. The interposer 30 may have a substrate including a semiconductormaterial. Alternatively, the interposer 30 may include a composite ofone or more support layers and one or more interconnect layers. The“support layers” may include material provided for a purpose other thanpurely electrical interconnection or electrical isolation. For instance,the support layers may include an acoustic backing material configuredto dampen acoustical reflections. In other applications, the supportlayers may include materials with desirable thermal properties. In stillother applications, the support layers may include materials configuredto provide further mechanical support.

The interposer 30 may also be fabricated from a material comprising oneof a polyimide, an aramid, a fluorocarbon, or a polyester. Furthermore,the interposer 30 may include a multi-layer interconnect systemconfigured to facilitate electrical coupling between the plurality oftransducers 18 and an electronic device which may be coupled to thebackside of the interposer 30, as described further below. Additionally,the interposer layer 30 may be attached to another layer via the solderbumps 32 or alternate interconnect structures positioned on a side ofthe interposer 30.

Turning now to FIG. 3, the interposer 30 of FIG. 2 is illustrated asincluding a first side 34 and a second side 36. Furthermore, theinterposer 30 also includes a length 38 and a width 40, which may beapproximately equivalent to a length and width of the substrate 12. Thefirst side 34 of the interposer 30 includes a plurality of connectors42. In one exemplary embodiment, the connectors 42 may comprise viashaving metal disposed therein to provide an electrical path from thefirst side 34 to the second side 36. As will be appreciated by thoseskilled in the art, an anisotropic or an isotropic electricallyconductive adhesive, such as a paste or film, may be disposed over thefirst side 34 of the interposer 30 to provide a physical, as well aselectrical connection between the interposer 30 and the substrate 12.Alternatively, an electrically conductive paste or metal, such assolder, may be disposed on each of the connectors 42 to provide amechanism for coupling the interposer 30 to the substrate 12. Theconnectors 42 on the first side 34 of the interposer 30 may be employedto connect the interposer 30 to the connectors of a device to which theinterposer is to be attached. For example, the connectors 42 positionedon the first side 34 of the interposer 30 enable the coupling betweenthe interposer 30 and connectors on the backside 16 of the substrate 12.Additionally, metal to metal interconnect may be formed employingthermal, ultrasonic or thermosonic bonding.

FIG. 4 illustrates the second side 36 of the interposer 30. Connectors44 that are formed on the second side 36 of the interposer 30 enable thecoupling between the second side 36 of the interposer 30 and a componentto which the interposer 30 is coupled, such as control and amplifierelectronics, as described further below.

According to one embodiment of the present technique, the X-Y plane isemployed for patterning the transducer elements 18 to facilitate theconstruction of large area transducer arrays. Conventionally, thecontrol and amplifier electronics employed to drive the individualtransducers are also positioned in the X-Y plane resulting in a largefootprint. Moreover, it is desirable to minimize interconnect lengths inorder to circumvent poor performance associated with longer interconnectlengths, such as, effects of capacitance, and degraded signal quality.

The performance of the transducer array 26 may be greatly enhanced byminimizing the interconnect lengths between the transducer elements 18and the associated amplifier and control electronics, which may beachieved by positioning the electronic devices in close proximity to thetransducer elements 18 in the Z-direction 24. The method of growing thetransducer array 26 in the Z-direction 24 results in the formation of athree-dimensional transducer array, to implement high volumetricdensity.

Large area transducer arrays 26 entail control and amplification of theindividual transducer elements 18. Generally, the control and amplifierelectronic devices are built employing semiconductor processing such asa Complementary Metal Oxide Semiconductor (CMOS) process. However, thesemiconductor processing for the electronics may yield differently thanthe large area transducer array. Typically, the electronics yield isbetter at the center of the wafer than at the edges of the wafer.Therefore, it may be advantageous to fabricate the electronics elementsseparately from the transducer elements 18, using any desirableprocessing method, and coupling the electronics array or individualelectronic devices to the second side 36 of the interposer 30. Byfabricating the electronics array separately and isolating theelectronics array to a layer other than that of the transducer array,optimal fabrication techniques may be chosen for each array. As with thetransducer array, the electronic devices that make up the electronicsarray may be tested such that the known good die may be implemented. Aswill be appreciated, the corresponding smaller electronic devices may bestacked, in the Z-direction 24, in close proximity to the individualtransducer elements 18 to form a fully functional large area transducerarray 26, as illustrated further below with respect to FIGS. 5-7.

FIG. 5 illustrates an exemplary embodiment of a stacking assembly 46. InFIG. 5, an electronics array formed as a single electronic device 48 isillustrated as being stacked under the transducer array 26, in theZ-direction 24. The electronic device 48 may include control andamplifier devices, for instance. As illustrated in FIG. 5, thetransducer elements 18 may be tiled on the front side 14 (see FIG. 1) ofa substrate 12. Furthermore, as illustrated in a presently contemplatedconfiguration, the stacked assembly 46 may also include an interposer30, which includes a multi-layer interconnect system. The interposer 30is employed to facilitate the electrical coupling between the pluralityof transducers 18 and the electronic device 48. Alternatively, thetransducer elements 18 may also be patterned directly on the interposer30, according to one aspect of the present technique. Furthermore, amulti-layer interconnect disposed on the substrate 12 may also sufficeto provide the coupling between the transducer elements 18 and theelectronic device 48. The electronic device 48 may be a signalprocessor.

In order to minimize the adverse effects of long interconnect lengths,the associated electronics are positioned directly below the transducerelements 18. In a presently contemplated configuration, as shown in FIG.6, a second stacked three-dimensional assembly 50 is illustrated asincluding a plurality of transducers 18 disposed on the front side 14(see FIG. 1) of a substrate 12, an interposer 30 through which amulti-layer interconnect system is fabricated, and an electronics arraythat includes a plurality of stacked electronic devices 52. Furthermore,according to an aspect of the present technique, an electronics arrayformed as a plurality of stacked electronic devices 52 is illustrated inFIG. 6. The multi-layer interconnect system disposed on the interposer30 facilitates electrical coupling between the individual transducerelements 18 positioned on the front side 14 of the substrate 12 and theassociated electronic devices 52. According to a further aspect of thepresent technique, the electronic devices 52 are shown as beingpositioned directly below the associated transducer element 18 that thestacked electronic device 52 is configured to drive.

The stacked electronic devices 52 may include a multi-layer,three-dimensional stack of various amplifier and control electronicsthat may be employed to drive the individual transducer elements 18 ofthe transducer array 26. According to one aspect of the presenttechnique illustrated in FIG. 7, an exemplary embodiment of stacking aplurality of electronic devices to form stacked electronic devices 52 isprovided. FIG. 7 illustrates the stacked electronic device 52 asincluding four separate layers of electronic devices. For example, afirst layer 54 may include high-voltage analog circuits. Furthermore, asecond layer 56 may include an array of pursers. In addition, a thirdlayer 58 may be an array of beam formers. Also, a fourth layer 60 mayinclude signal processors. Additionally, layer-to-layer interconnect maybe accomplished by means of a plurality of through-hole vias 62 locatedalong the periphery of the electronic device layers 54, 56, 58 and 60.Moreover, as illustrated in FIG. 7, the four layers 54, 56, 58 and 60are stacked one on top of the other in a direction 64 that is theZ-direction 24. Alternatively, the through-hole vias 62 may be arrangedin other configurations, such as through the middle region of each layer54, 56, 58 and 60. As will be appreciated, any suitable means ofelectrically connecting each of the layers 54, 56, 58 and 60 may beimplemented.

The placement or stacking of the electronic devices 52, on the backsideof a large area transducer array 26 may provide advantages to circumventissues related with long interconnect lengths. It may be desirable toalign the stacked electronic devices 52 with the associated transducerelement 18. Pre-fabricated spacers (not shown) may be employed to alignthe stacked electronic devices 52 in a more precise grid on the backsideof the transducer array 26, according to another embodiment of thepresent technique, as described further with respect to FIG. 8.Furthermore, materials properties of the transducer, electronics, andinterconnect materials may be chosen or utilized to facilitate precisionalignment and assembly of the transducer arrays with stackedelectronics.

FIG. 8 is a flow chart 66 illustrating steps for aligning the stackedelectronic device 52 (see FIG. 6) with an associated transducer element18 (see FIG. 6), in accordance with one embodiment. The methodsummarized in FIG. 8 begins at step 68 where the positioning of thestacked electronic device 52 is performed. The stacked electronic device52 is positioned along the Z-direction 24 (see FIG. 6) with respect tothe transducer element 18 that the stacked electronic device 52 isconfigured to drive.

Following step 68, step 70 is performed. In step 70, pre-fabricatedspacers may be employed to space the plurality of stacked electronicdevices 52 in a precise grid on the backside of the transducer array 26(see FIG. 6).

Subsequently, step 72 is performed where the electronic device 52 iscoupled to the corresponding transducer element 18. The coupling of theelectronic device 52 to the corresponding transducer element 18 may beaccomplished by means of interconnect activation methods, such as, butnot limited to, heat and pressure for solder reflow.

Step 74 involves the realignment of the pre-fabricated spacers in orderto align the transducer elements 18 with their corresponding stackedelectronic devices 52. Subsequent to performing the activation step 72,gaps may arise in the alignment between the individual transducerelements 18 and the relevant electronic devices 52. The temporaryspacers may now be realigned to reduce the gaps that have arisen duringthe activation step 72. In certain sensor applications the gaps in thetransducer array 26 may be acceptable. However, the gaps between thestacked electronic devices may be filled with materials that enhance theperformance of the transducer. For instance, in an acoustic transducer,acoustic damping material may be disposed within the gaps and positionedto minimize acoustic reflections in the gap.

The large area transducer array 26 and the method of constructing thelarge area transducer array 26 described hereinabove enable thefabrication of three-dimensional, large area transducer arrays, whichmay find application in various fields such as medical diagnosticsystems, medical and industrial imaging and the non-destructiveevaluation and inspection of materials and structures. Furthermore,employing multi-layer interconnect systems disposed either on thesubstrate 12 or on the interposer 30, greatly facilitates the assemblyand performance of transducers and electronics with high densities ofI/O connectors.

In addition, by positioning the electronic devices 52 in close proximityto the transducer elements 18, the system function and performance maybe greatly enhanced. Such improvements are a consequence of minimizedinterconnect lengths and appropriate alignment of the electronic devices52 with the associated transducer elements 18. Moreover, stacking theassociated electronic devices 52 in the Z-direction 24 results in higherfunctional density for a given package volume. Still further, by formingpackages wherein each of the functional blocks of the package isisolated by fabrication in a separate layer, optimized fabricationtechniques for each type of functional block may be implemented.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A method for fabricating a tiled transducer array, the methodcomprising: fabricating a wafer comprising a plurality of transducers;dicing the wafer to form individual transducers; testing the individualtransducers to identify a plurality of known good transducers; preparinga substrate having a front side and a backside, wherein the backside ofthe substrate comprises a plurality of connectors; positioning theplurality of known good transducers on the front side of the substrateand aligning the plurality of transducers in a horizontal direction anda vertical direction to form a transducer array; and electricallycoupling the connectors on the substrate to the plurality of known goodtransducers, wherein the connectors are arranged such that each of theplurality of known good transducers may be electrically coupled to anelectronic device disposed on the backside of the substrate, through arespective one or more of the plurality of connectors.
 2. The method ofclaim 1, comprising connecting the electronic device to the plurality ofknow good transducers via the connectors.
 3. The method of claim 1,wherein the substrate comprises a semiconductor material.
 4. The methodof claim 1, wherein the substrate comprises a flexible material.
 5. Themethod of claim 1, wherein positioning the plurality of known goodtransducers on the front side of the substrate and aligning theplurality of transducers in the horizontal direction and the verticaldirection to form the transducer array comprises aligning thetransducers in the horizontal direction with a spacer.
 6. The method ofclaim 5, comprising aligning the transducers with the electronic deviceby realigning the spacers with the electronic device after connectingthe electronic device to the plurality of known good transducers.
 7. Themethod of claim 1, comprising coupling a support layer configured todampen acoustic reflections to the substrate.
 8. The method of claim 1,wherein a transducer in the plurality of transducers comprises a lightsensor.
 9. The method of claim 1, wherein a transducer in the pluralityof transducers comprises a heat sensor.
 10. The method of claim 1,wherein a transducer in the plurality of transducers comprises anacoustic sensor.
 11. A method for fabricating a stackedthree-dimensional transducer array, the method comprising: obtaining asubstrate having a front side, a backside, and an electricalinterconnect providing an electrical path from the front side of thesubstrate to the backside of the substrate; disposing a plurality oftransducers on the front side of the substrate; and coupling theplurality of transducers on the front side of the substrate to anassociated electronic device on the backside of the substrate throughthe electrical interconnect.
 12. The method of claim 11, furthercomprising positioning an interposer between the plurality oftransducers and the electronic device.
 13. The method of claim 11,wherein the stacked transducer array is a three-dimensional array.
 14. Amethod of aligning a plurality of electronic devices with a plurality oftransducers in a transducer array disposed generally in an X-Y plane,the method comprising: positioning each of a plurality of electronicdevices so they are aligned in a direction; aligning each of theplurality of transducers with at least one of the plurality ofelectronic devices via a pre-fabricated spacer; and coupling each of theplurality of electronic devices to the transducer array via aninterconnect.
 15. The method of claim 14, wherein positioning comprisesstacking the electronic devices in the direction.
 16. The method ofclaim 14, wherein the direction is the Z-direction.
 17. The method ofclaim 14, further comprising realigning the pre- fabricated spacers toadjust gaps between each of the plurality of transducers and the atleast one of the plurality of electronic devices.
 18. The method ofclaim 14, further comprising coupling the plurality of electronicdevices and the plurality of transducers to a non-destructive testingsystem.
 19. The method of claim 14, further comprising coupling theplurality of electronic devices and the plurality of transducers to animaging system.
 20. The method of claim 19, wherein the imaging systemcomprises an x-ray imaging system.